Last summer I had to purchase a new gas container and much to my surprise, ALL the spouts on the new containers have weird "locks" on them. I guess it was supposed to prevent leaking, spillage, or whatever- but only made things waaay more cumbersome to pour gas into my lawnmower. In fact, it's even caused me to overflow my mower's reservoir every single time, because the gas won't release until you invert the container and press the spout down along the side of the reservoir. Which means you can't see the gas as it flows into the mower, and can't really tell when to stop, till it overflows. What a strange "upgrade". I pretty much checked all the big box hardware stores and other small ones, plus online of course. Same thing. The old simple basic tubular spouts were all phased out. Therefore I created one.

I printed mine in Bridge Nylon (but I think any kind of nylon should work), which supposedly is one of the best filaments for withstanding chemical substances. Not so great for being submerged in water, so I would recommend leaving it affixed outside of the container. Temporary flows of liquid (gas or otherwise) should not effect it, which has been my experience thus far. As the pictures show, I also used a rubber washer on the base for a tight seal (permanently attached with weatherproof superglue).

The existing caps for older containers, plus the new ones seemed to fit fine, but I created a file for that as well.

The spout should fit both 2 and 5 gallon containers. Perhaps even smaller and larger ones too (the pictures show a 2 gallon).

I would recommend 100% infill.